Keep it in D (not manual mode) and use the +/- by pressing the - and it will not allow the truck to shift to 6th gear.

WEMig is right. that's all it takes to "lock out" a gear, or gears.

Your bars may be a little light. I have 800 - 1200# and they work well with our 30WIKSS.

I have the F250, 6.2L supercab and got 8.3 over 700 miles from NE Louisiana to Pigeon Forge, TN. I am real impressed with this setup. Great on flat land but really strong in the mountains. I found it interesting that mileage actually got better in the mountains.

I didn't have any water in the fresh tank because I thought my tongue weight was light, turns out its at 15%, but I like to travel with about a half a tank for road side stops so I'm going to do that on the way back and see how she does. The fresh water tank is behind the axles so that should lighten my tongue weight some. Thanks for the input.

I had a 97 CC 4x4 with the 7.3 and it was a great truck and got excellent fuel mileage, hold on to the one you have. I just couldn't justify the extra $9000 for one of the new 6.7L diesels but they are nice. I figure the way I use my truck it will cost me an extra $500 a year in gas over what I would pay if I had diesel. That's about 18 years before I lose money. Fuel mileage isn't an issue for me I was just sharing for other folks that might be curious. As far as burning rubber, I haven't had a desire to do that in a long time but blowing smoke is a different story :-). Happy camping!

I have a F 150 with a 6.2. It gets similar mileage as your F 250 pulling a 5th wheel. I find that it can get as little as 6.5 mpg and as high as 10 mpg depending on the direction and speed of the wind. However, It has plenty of stuff to get the job done and keeps up with the 18 wheelers. It can go 70 mph but it just runs better at 65. I am retired so what is the hurry? It works best when the cruise control is off. I chose the 6.2 over the ecoboost V6. I figure there is more braking capacity with the 6.2 in the mountains. I am told that my F 150 should never pull a 5th wheel, but it works for me. It has every towing option available from the factory.

I have a F 150 with a 6.2. It gets similar mileage as your F 250 pulling a 5th wheel. I find that it can get as little as 6.5 mpg and as high as 10 mpg depending on the direction and speed of the wind. However, It has plenty of stuff to get the job done and keeps up with the 18 wheelers. It can go 70 mph but it just runs better at 65. I am retired so what is the hurry? It works best when the cruise control is off. I chose the 6.2 over the ecoboost V6. I figure there is more braking capacity with the 6.2 in the mountains. I am told that my F 150 should never pull a 5th wheel, but it works for me. It has every towing option available from the factory.

How do you figure you have more braking capacity with a v8 compared to a v6. The brakes are the same no matter what engine you have.

I didn't realize you could order a F150 with that much payload, so I decided a F250 was the way to go. I originally started this thread because I had read that someone else was having issues towing the same model Flagstaff as mine. Im learning that not all trailers are created equal, duh. My next trailer will be a 5er, I think I will enjoy towing it better, but you never know. My first trailer was a 5er and it towed very well. I was thinking my trailer didnt have enough tongue weight but after going to the scales it has plenty. On my trip back from the campsite I filled the fresh water tank which is at the very back of the trailer, but I couldn't tell much difference. You know That sucking feeling you feel when an 18 wheeler passes, I can actually feel that when a SUV passes. I have the feeling that sway will be an issue in high wind, we will see. Looks like "it is what it is", I had the same issues with the Tundra and thought the F250 would eliminate it but no luck.

I used to have a 2010 GM half ton with the towing package and 5.3 gas engine, it was a dog when it came to pulling our 5,000 lb bumper hitch Kodiak trailer, I couldn't stand driving it pulling the trailer, no power and terrible gas mileage. I traded the truck for a 2011 F250 diesel and the difference was incredible. This year we bought a used Flagstaff 26' 5th wheel, and I can easily cruise at 60 mph, with hardly a downshift, although in the mountains or in town I use tow/haul mode. I have the 5th wheel hitch package, and it is one of the best options I purchased with the truck, although at the time of purchase I didn't have a need for it. I love driving my truck, and for a relatively heavy truck, the gas mileage is great, I can easily get 25mpg (Imperial gallon) when I'm not towing, and about 17 mpg with my trailer. Now that I've got a new set of trailer tires, a new TPMS, and a truck that will tow, I'm a happy camper.